Process of preparing conducting-filaments.



H. D. MADDEN &'W. G. HOUSKBBPER. i

PROCESS OF PREPARING CONDUCTING FILAMENTS. APPLICATION FILED MAR. 31, 1909.

1,099,095, I Patented June 2, 191 i 112 r v V J W Z2 Z3 WITNESSES I INVENTORS ATT'ORNEY UNITED STATES PATENT OFFICE.

HARRY D. MADDEN, OF BLOOMFIEL D, NEW JERSEY, AND WILLIAM G. HOUSKEEPER,

OF PHILADELPHIA, PENNSYLVANIA, ASSIGNORS TO WESTINGHOUSE LAMP COM- PANY, A. CORPORATION OF PENNSYLVANIA.

PROCESS OF PREPARING CONDUCTING-FILAMENTS.

Specification of Letters Patent.

Patented June 2, 1914.

Application filed March 31, 1909. Serial No. 486,925.

To all whom it may concern: Be it known that we, HARRY D. MADDEN and WILLIAM G; HOUSKEEPER, citizens of the United States, and residents, respectively, of Bloomfield, in the county of Essex and State of New Jersey, and of Philadelhia, in the county of Philadelphia and State of Pennsylvania, have invented a new and useful Improvement in Processes of Preparing Conducting-Filaments, of which the following is a specification.

Our invention relates to processes of preparing conducting filaments to be embodied in incandescent lamps;

The'object of the invention is to provide a process of the character indicated whereby very fine filaments, such as filaments composed of or containing tungsten or similar material or materials, may be prepared con tinuously and in considerable lengths.

It has heretofore been customary, in the preparation of tungsten filaments, to first reduce the material of which the filament is composed into filament form in comparatively short lengths, which .are bent into zigzag shape and laid upon papers or trays for drying, the filaments being thereafter severed into U or hair-pin shaped pieces, that are next carbonized, and then heated to gradually increasing degrees, by the passage of current therethrough, while supported between terminals within a chamber containing a suitable forming gas. This process has required a large number of separate and independent operations, and, in practising it, it has been impracticable, or impossible, to produce the filaments in any considerable lengths, with the result that it has heretofore been deemed quite necessary to use only hair-pin shaped filaments in the construction of lamps. There has also been considerable breakage and waste incident to the handling of the filaments in the various stages of the process of manufacture.

According to the present invention, filaments of uniform character may be produced continuously in considerable lengths, and with but a very small amount of attendance and handling, with the additional advantage that the filaments thus prepared may be employed, either in hair-pin form or in continuous pieces, in the construction of lamps. Although the invention is particularly useful in the production of filaments containing or composed of tungsten, it may also be employed with considerable advantage in the production of carbon or other filaments.

Figure 1 of the accompanying drawing is a partially structural and partially diagrammat c view of apparatus adapted to carry the invention intoefl'ect, some of the structural parts being shown in section for the sake of clearness of illustration. Figs. 2 and 3 are enlarged sectional views respectlvely of the filament press and of one of the terminal devices of the apparatus.

The material to be formed into filaments, which may be composed of any of the ingredients usually employed in the preparation of tungsten filaments, or of any other desired and suitable ingredients, is placed III a cylinder 1 having an apertured plate or die 2 in its lower end through which thematerial is forced'by means of a piston 3 for the pur ose of reducing it to filament form. As the lamentous material is extruded from the cylinder 1, it passes into the upper smaller end of a conicalshell or inverted funnel 4 within the lower open end of which is a gas burner 5, or other suitable heating means, whereby heat may beiapplied to the filament for the purpose of drying it. Since the filament is in a suspended position, there is no tendency for it to break as it contracts during the drying operation. Directly beneath the inverted funnel 4 is another substantially funnel-shaped member 6 through which the filament passes, and in which it is coiled when it is not drawn therefrom as rapidly as it is extruded from the cylinder 1, the funnel 6 being so shaped that, when the filament becomes coiled therein, its convolutions do not interfere with one another. ()ther suitable means may, of course, be employed for preventing tangling of the filament after it leaves the press.

As the filament leaves the funnel 6, it passes into and through a receptacle 8 constituting a forming chamber and containing a suitable gas, or mixture of gases, such as of nitrogen and hydrogen, the gas or' gases being supplied to the receptacle through a pipe 9. Within the receptacle 8, and directly beneath the entrance thereto, is a coil .10 that surrounds the filament and serves,

when traversed by current derived from any suitable source of energy, such as that shown at 11, to heat the filament sufficiently to carbonize it and increase its electrical conductivity. In some cases, it may not be necessary or desirable to carbonize the filament at this point, since it may already have a sufiicientdegree of conductivity, while, in other cases, it may be desirableto employ other suitable heating or carbonizlng means than the coil 10.

Adjustably mounted upon an insulating rod 12 within the forming chamber, and arranged in alinement with each other and with the entrance and exit to the chamber, is a series of terminal devices 13, 14:, 15, 16, 17,18 and 19 that are severally connected to the source of energy 11, the terminal 19 be ing connected to one side of the circuit, and the other terminals being connected to the other side of the circuit. Included in each of the connections to the terminal devices is a suitable variable resistance element 20, and, in the connections to the terminal devices 13 to 18, inclusive, there are also included one or more lamps 21, the resistance devices and the lamps being provided for the purpose of permitting independent adjustment of the amount of current supplied to the portions of the filament intermediate adjacent terminal devices, and also of the total amount of current that traverses the filament. Each of the terminal devices 13 to 19, inclusive, comprises an apertured member 22, preferably composed of copper, the portions of which, adjacent to the aperture, are amalgamated in order to increase the capillary action between the member and a body of mercury 23 that substantially fills and extends across the aperture.

The filament passes through-the apertures of the terminal devices and through the bodies of mercury that extend across the apertures and make electrical contact with the filament, the surface tensions of the bodies of mercury serving to maintain the same within the apertures in the members 22 even during the progressive longitudinal movement of the filament. In order that the surface tension of each body of mercury may also serve to cause the filament to pass through the central portion thereof and to maintain the filament out of engagement with the member 22, the face of each body is rendered concave in form, by wiping or otherwise carefully removing the excess thereof from both sides of the apertured member 22.

It follows that, as the filament passesthrough the forming chamber, currents of electricity are supplied to different portions thereof, and, since all butone of the terminal devices 13 to 19, inclusive", are connected lating the resistances included in the connections to the terminal devices. The filament is, in this manner gradually heated until the final degree of heat is sufficient to treat the material of which the filament is composed and to thereby complete the preparation or forming process. Durin the operation of the apparatus, the terminal devices may become heated, and, accordingly, in order to limit the temperature thereof, it may be desirable to provide cooling coils 24:

adjacent to certain of the terminals, thecooling coils being traversed by water, or some other suitable medium.

The filament is drawn through the forming chamber at a suitable rate by means of a pair of rollers 25 that are driven by means of an electric motor 26, or otherwise, and the filament may be wound, as it is completed, upon a reel 27, that may also be actuated by the motor, or otherwise, or it may be coiled or disposed of by other suitable means. Since it is desirable to prevent the escape of the forming gas from the forming chamber, the entrance thereto is sealed by means of a body of mercury 28 that is supported in substantially the same manner as the bodies of mercury constituting parts of the terminals 13 to 19, inclusive.

We claim as our invention:

1. The process of preparing a filament which consists in applying different amounts of electric current to different portions of a filamentous material.

2. The process of preparing a filament which consists in applying gradually increasing amounts of electric current to successive portions of a filamentous material.

3. The process of preparing a filament which consists in progressively moving a filamentous material and applying gradually increasing amounts of electric current to the material, as it progresses.

4. The process of preparing a filament which consists in progressively moving a filamentous material and applying different amounts of electric current to the material, in different stages of its progression.

5. The process of preparing a filament which consists in progressively moving a .filamentous material within an inert atmosprogressively moving the filament, while drying it, and applying thereto different amounts of electric current, in diflerent stages of its progression.

8. The process of preparing a filament which consists in converting the unprepared material to continuous filament form, and progressively -moving the filament, while drying it, and applying thereto increasing amounts of electric current, as it progresses. 9. The process of preparing'a filament which consists in longitudinally moving a filamentous material and simultaneously applyin different amounts of electric current to cli erent portions thereof.

10. The process of treating filamentary structures which consists in passing different amounts of electric currents through successive portions thereof, and in maintaining the same in heated condition between the said successive portions. r

In testimony whereof, we have hereunto subscribed our names this twentieth day of March, 1909. v Q

HARRY D. MADDEN WILLIAM G. HOUSKEEPER.

Witnesses:

' R. C. KARCHNER,

W. R. UMBACH. 

